Implemented module support

* module support aims to enable extraction of core static site generation functionality implemented for my personal blog into a separate project
** i.e. the detail transformations of repository [blog.kummerlaender.eu](https://github.com/KnairdA/blog.kummerlaender.eu/)
* a BuildXSLT module is a simple XML file definining the transformations which make up the module
* modules may be built using the newly implemented "module" task type
** this task requires a input and definition node
*** the input node is resolved in the same way as "generate" input nodes
*** the definition node currently only supports the file mode
** chained transformation links inside the definition are resolved relative to the definition files location
*** this was enabled by commit `a4a7ee4` to InputXSLT
* restructured task processing
* transformations are now read by "InputXSLT:generate" instead of by "InputXSLT:read-file"
** this enables entities to be resolved against the transformation location
** this was enabled through filesystem context resolution changes in commit `3c166ed` to InputXSLT
* added basic error handling based on terminating XSLT messages

1 files changed, 176 insertions, 14 deletions

diff --git a/build.xsl b/build.xsl
index bd57c40..585cb12 100644
--- a/build.xsl
+++ b/build.xsl
@@ -18,10 +18,23 @@
 	<xsl:param name="input"/>
 	<xsl:param name="transformation"/>
 
-	<xsl:copy-of select="InputXSLT:generate(
+	<xsl:variable name="result" select="InputXSLT:generate(
 		xalan:nodeset($input),
-		InputXSLT:read-file(string($transformation))/self::file/node()
-	)/self::generation/node()"/>
+		string($transformation)
+	)/self::generation"/>
+
+	<xsl:choose>
+		<xsl:when test="$result/@result = 'success'">
+			<xsl:copy-of select="$result/node()"/>
+		</xsl:when>
+		<xsl:otherwise>
+			<xsl:message terminate="yes">
+				<xsl:text>Failed to generate transformation "</xsl:text>
+				<xsl:value-of select="string($transformation)"/>
+				<xsl:text>"</xsl:text>
+			</xsl:message>
+		</xsl:otherwise>
+	</xsl:choose>
 </xsl:template>
 
 <xsl:template name="generate_chain">
@@ -51,22 +64,97 @@
 	</xsl:choose>
 </xsl:template>
 
-<xsl:template match="task[@type = 'generate']">
-	<xsl:variable name="input">
+<xsl:template name="augment_transformation">
+	<xsl:param name="base"/>
+	<xsl:param name="transformation"/>
+
+	<transformation mode="{$transformation/@mode}">
 		<xsl:choose>
-			<xsl:when test="input/@mode = 'embedded'">
-				<xsl:copy-of select="input/node()"/>
+			<xsl:when test="$transformation/@mode = 'file'">
+				<xsl:value-of select="$file/@base"/>
+				<xsl:text>/</xsl:text>
+				<xsl:value-of select="$transformation/text()"/>
 			</xsl:when>
-			<xsl:when test="input/@mode = 'file'">
-				<xsl:copy-of select="InputXSLT:read-file(input/text())/self::file/node()"/>
+			<xsl:when test="$transformation/@mode = 'chain'">
+				<xsl:for-each select="$transformation/link">
+					<link>
+						<xsl:value-of select="$base"/>
+						<xsl:text>/</xsl:text>
+						<xsl:value-of select="text()"/>
+					</link>
+				</xsl:for-each>
 			</xsl:when>
+			<xsl:otherwise>
+				<xsl:copy-of select="$transformation/node()"/>
+			</xsl:otherwise>
 		</xsl:choose>
-	</xsl:variable>
+	</transformation>
+</xsl:template>
+
+<xsl:template name="read_module">
+	<xsl:param name="path"/>
+
+	<xsl:variable name="file" select="InputXSLT:read-file($path)/self::file"/>
+
+	<xsl:choose>
+		<xsl:when test="$file/@result = 'success'">
+			<xsl:choose>
+				<xsl:when test="name($file/node()) = 'transformation'">
+					<xsl:call-template name="augment_transformation">
+						<xsl:with-param name="base"           select="$file/@base"/>
+						<xsl:with-param name="transformation" select="$file/node()"/>
+					</xsl:call-template>
+				</xsl:when>
+				<xsl:otherwise>
+					<xsl:copy-of select="$file/node()"/>
+				</xsl:otherwise>
+			</xsl:choose>
+		</xsl:when>
+		<xsl:otherwise>
+			<xsl:message terminate="yes">
+				<xsl:text>Failed to resolve module "</xsl:text>
+				<xsl:value-of select="$path"/>
+				<xsl:text>"</xsl:text>
+			</xsl:message>
+		</xsl:otherwise>
+	</xsl:choose>
+</xsl:template>
+
+<xsl:template name="resolve_module">
+	<xsl:param name="input"/>
+	<xsl:param name="definition"/>
 
 	<xsl:choose>
-		<xsl:when test="transformation/@mode = 'chain'">
+		<xsl:when test="$definition/@mode = 'file'">
+			<xsl:variable name="module">
+				<xsl:call-template name="read_module">
+					<xsl:with-param name="path" select="$definition/text()"/>
+				</xsl:call-template>
+			</xsl:variable>
+
+			<xsl:call-template name="handle_generate">
+				<xsl:with-param name="input"          select="$input"/>
+				<xsl:with-param name="transformation" select="xalan:nodeset($module)/transformation"/>
+			</xsl:call-template>
+		</xsl:when>
+		<xsl:otherwise>
+			<xsl:message terminate="yes">
+				<xsl:text>Failed to resolve module definition mode "</xsl:text>
+				<xsl:value-of select="$definition/@mode"/>
+				<xsl:text>"</xsl:text>
+			</xsl:message>
+		</xsl:otherwise>
+	</xsl:choose>
+</xsl:template>
+
+<xsl:template name="resolve_transformation">
+	<xsl:param name="input"/>
+	<xsl:param name="transformation"/>
+
+	<xsl:choose>
+		<xsl:when test="$transformation/@mode = 'chain'">
 			<xsl:variable name="chain">
-				<xsl:for-each select="transformation/link">
+				<xsl:for-each select="$transformation/link">
 					<xsl:sort select="position()" data-type="number" order="descending"/>
 
 					<xsl:copy-of select="."/>
@@ -79,13 +167,87 @@
 				<xsl:with-param name="tail"  select="xalan:nodeset($chain)/link[position() &gt; 1]"/>
 			</xsl:call-template>
 		</xsl:when>
-		<xsl:when test="transformation/@mode = 'file'">
+		<xsl:when test="$transformation/@mode = 'file'">
 			<xsl:call-template name="generate">
 				<xsl:with-param name="input"          select="$input"/>
-				<xsl:with-param name="transformation" select="transformation/text()"/>
+				<xsl:with-param name="transformation" select="$transformation/text()"/>
 			</xsl:call-template>
 		</xsl:when>
+		<xsl:otherwise>
+			<xsl:message terminate="yes">
+				<xsl:text>Failed to resolve transformation mode "</xsl:text>
+				<xsl:value-of select="$transformation/@mode"/>
+				<xsl:text>"</xsl:text>
+			</xsl:message>
+		</xsl:otherwise>
 	</xsl:choose>
 </xsl:template>
 
+<xsl:template name="resolve_input">
+	<xsl:param name="input"/>
+
+	<xsl:choose>
+		<xsl:when test="$input/@mode = 'embedded'">
+			<xsl:copy-of select="$input/node()"/>
+		</xsl:when>
+		<xsl:when test="$input/@mode = 'file'">
+			<xsl:copy-of select="InputXSLT:read-file($input/text())/self::file/node()"/>
+		</xsl:when>
+		<xsl:otherwise>
+			<xsl:message terminate="yes">
+				<xsl:text>Failed to resolve input mode "</xsl:text>
+				<xsl:value-of select="$input/@mode"/>
+				<xsl:text>"</xsl:text>
+			</xsl:message>
+		</xsl:otherwise>
+	</xsl:choose>
+</xsl:template>
+
+<xsl:template name="handle_generate">
+	<xsl:param name="input"/>
+	<xsl:param name="transformation"/>
+
+	<xsl:call-template name="resolve_transformation">
+		<xsl:with-param name="input">
+			<xsl:call-template name="resolve_input">
+				<xsl:with-param name="input" select="$input"/>
+			</xsl:call-template>
+		</xsl:with-param>
+		<xsl:with-param name="transformation" select="$transformation"/>
+	</xsl:call-template>
+</xsl:template>
+
+<xsl:template name="handle_module">
+	<xsl:param name="input"/>
+	<xsl:param name="definition"/>
+
+	<xsl:call-template name="resolve_module">
+		<xsl:with-param name="input"      select="$input"/>
+		<xsl:with-param name="definition" select="$definition"/>
+	</xsl:call-template>
+</xsl:template>
+
+<xsl:template match="task[@type = 'generate']">
+	<xsl:call-template name="handle_generate">
+		<xsl:with-param name="input"          select="input"/>
+		<xsl:with-param name="transformation" select="transformation"/>
+	</xsl:call-template>
+</xsl:template>
+
+<xsl:template match="task[@type = 'module']">
+	<xsl:call-template name="handle_module">
+		<xsl:with-param name="input"      select="input"/>
+		<xsl:with-param name="definition" select="definition"/>
+	</xsl:call-template>
+</xsl:template>
+
+<xsl:template match="task">
+	<xsl:message terminate="yes">
+		<xsl:text>Failed to handle task type "</xsl:text>
+		<xsl:value-of select="@type"/>
+		<xsl:text>"</xsl:text>
+	</xsl:message>
+</xsl:template>
+<xsl:template match="text()|@*"/>
+
 </xsl:stylesheet>